Snow tires are traditionally equipped with stud pins installed in the tread portion of the tire to allow the tire to grip an icy road surface.
Typically, a stud pin is embedded into a stud pin installation hole provided in the tread portion of the tire. The stud pin broadens a pin bore and is tightly embedded therein so that the stud pin does not fall out of the stud pin installation hole due to braking, driving, or lateral forces received from the road surface while the tire is moving.
Tire spikes (stud pins) are a known implementation of a lighter-weight stud pin that improves performance on icy surfaces (International Patent Application Publication WO/2012/117962). The aforementioned stud pin is provided with a pillar and a pin. The pillar is fitted from one end in a central axis direction into a close-ended hole formed in the tread surface of the tire and attached to the tread surface; and the pin protrudes from the other surface in the central axis direction of the pillar. Removing the portion of the pillar between the other end surface of the circular pillar protruding from the other end surface of and extending along the central axis direction of the pillar and the surrounding surface forms an irregularly shaped pillar that constitutes the pin having cavities.
However, studded snow tires move not only on icy road surfaces;
studded snow tires are also on concrete road surfaces or asphalt road surfaces, which are harder road surfaces compared to icy road surfaces, so the stud pins drop out comparatively frequently.
Even for tires equipped with the above-mentioned stud pins, there are cases where the stud pins often fall out (pin drop) due to the forces on the tire while a vehicle is driving, breaking, or cornering on a concrete or asphalt road. There will be a large amount of pin drop if there is any clawing force applied between the stud pin and the road surface, the clawing force overcomes the force retaining the stud pin in the tread rubber material of the tire. Therefore, there is a demand for further improvement regarding pin drop for these pneumatic stud tires.